Industrial silicon surface modification method based on plasma-assisted technology

Abstract

The invention relates to the field of industrial silicon surface modification, and discloses an industrial silicon surface modification method based on a plasma-assisted technology, which comprises the following steps: (a) placing an industrial silicon substrate in a vacuum reaction cavity of plasma processing equipment; (b) introducing a multi-component mixed gas composed of at least two gases into the vacuum reaction cavity; (c) exciting plasma, and performing modification treatment on the surface of the industrial silicon by regulating and controlling the power and frequency of a plasma source, the proportion and flow of the multi-component mixed gas and the treatment time; and (d) forming the nano-composite structure on the surface of the industrial silicon in situ by utilizing a synergistic effect between different physical and chemical processes in the multi-component mixed gas plasma. Compared with the prior art, the method has the advantages that the nano-composite structure is formed on the surface of the industrial silicon in situ through the synergistic effect in the multi-component mixed gas plasma, so that integration of multiple functional characteristics is realized at one time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial silicon surface modification, and particularly relates to an industrial silicon surface modification method based on plasma-assisted technology. BACKGROUND

[0002] Industrial silicon is a basic material in the fields of photovoltaics, electronic information and chemical catalysis, and its surface properties directly affect the performance of devices. In photovoltaic applications, the cleanliness and hydrophilicity of the surface of a silicon wafer affect the quality of the texturing structure and antireflection film, and further affect the photoelectric conversion efficiency; in electronic packaging, the silicon substrate is required to have extremely low surface resistance to reduce signal loss; in the field of catalysis, the original silicon surface is inert and difficult to be directly used as a high-efficiency catalyst carrier.

[0003] At present, methods for improving the surface properties of silicon include wet chemical treatment and physical vapor deposition. These methods have limitations: wet chemical treatment produces chemical waste liquid and is difficult to achieve uniform modification on the rough or porous surface of industrial silicon; physical vapor deposition can prepare functional thin films, but has weak adhesion, high process temperature, and is difficult to integrate multiple functions.

[0004] Plasma surface modification technology has the advantages of dry processing, low temperature and environmental protection. In the prior art, there are reports of using single gas (such as oxygen or carbon tetrafluoride) plasma to treat high-purity semiconductor silicon wafers for single function (such as hydrophilization or hydrophobization). However, industrial silicon usually contains impurities and has high surface roughness, and single-function plasma treatment cannot meet the complex requirements of surface properties in high-tech applications. SUMMARY

[0005] (I) Technical problems to be solved

[0006] The technical problem to be solved by the present application is to provide an industrial silicon surface modification method based on plasma-assisted technology, which forms a nano-composite structure on the surface of industrial silicon in situ through the synergistic effect of a multi-component mixed gas plasma, thereby integrating multiple functional properties at one time.

[0007] (II) Technical solutions

[0008] To solve the above technical problems, the technical solution provided by the present application is as follows: an industrial silicon surface modification method based on plasma-assisted technology, comprising the following steps:

[0009] (a) placing an industrial silicon substrate in a vacuum reaction cavity of a plasma treatment device;

[0010] (b) introducing a multi-component mixed gas composed of at least two gases into the vacuum reaction cavity;

[0011] (c) exciting the plasma and modifying the surface of the industrial silicon by regulating the power, frequency, ratio and flow rate of the multi-component mixed gas and processing time of the plasma source;

[0012] (d) forming a nano-composite structure on the surface of the industrial silicon in-situ by the synergistic effect between different physical and chemical processes in the multi-component mixed gas plasma, thereby simultaneously imparting at least two functional properties to the surface of the industrial silicon; the functional properties are selected from super-hydrophilicity, high-temperature oxidation resistance, high conductivity, controllable hydrophobicity / super-hydrophobicity and catalytic activity.

[0013] As an improvement, the multi-component mixed gas comprises at least two combinations of argon, oxygen, nitrogen, hydrogen, carbon tetrafluoride, methane and ammonia.

[0014] As an improvement, in step (c), the power of the plasma source ranges from 50 W to 5000 W, the frequency ranges from 13.56 MHz to 2.45 GHz, and the processing time ranges from 10 seconds to 60 minutes.

[0015] As an improvement, in step (d), the nano-composite structure formed in-situ comprises a composite layer formed by embedding metal or non-metal compound nanoparticles generated by oxidation, nitridation or carbonization reaction into the silicon surface.

[0016] As an improvement, after step (a) and before step (b), the method further comprises a step of pretreating the industrial silicon substrate, wherein the pretreatment comprises at least one of mechanical polishing, chemical cleaning or ultrasonic cleaning to remove surface contaminants and natural oxide layers.

[0017] As an improvement, in step (c), a pulse-modulated plasma mode is used, and process parameters are regulated in real time by monitoring plasma emission spectrum to ensure processing uniformity.

[0018] As an improvement, in step (d), the super-hydrophilicity is manifested as a water contact angle less than 10°; and the high conductivity is manifested as a surface square resistance less than 100 Ω / □.

[0019] As an improvement, in step (d), the high-temperature oxidation resistance is manifested as a reduction of more than 30% in the oxidation weight gain per unit area of the modified industrial silicon after being kept at 800℃ in static air for 1 hour compared with the unmodified sample.

[0020] As an improvement, the modified industrial silicon material prepared by the method is suitable for photovoltaic cells, electronic packaging or chemical catalysis fields.

[0021] (Three) beneficial effects

[0022] The present application has the following advantages compared with the prior art: the present application introduces a multi-component mixed gas and regulates the plasma chemical reaction path, utilizes the synergistic effect between different active species (such as ions, radicals), and in-situ constructs a nano-composite structure on the surface of industrial silicon in one processing process. The nano-composite structure formed in the modification process, such as silicon nitride, silicon carbide or specific oxides, is in-situ generated on the surface of the silicon substrate by high-energy particle bombardment and chemical reaction of the plasma, and is strongly chemically bonded with the substrate, rather than physically attached. This bonding mode effectively avoids the risk of peeling off of the functional layer due to thermal stress or mechanical stress during use. DETAILED DESCRIPTION

[0023] The summary of the application will be further described in detail in combination with specific embodiments, but it should not be understood that the scope of the subject matter of the present application is limited to the following examples.

[0024] Example 1: Preparation of super-hydrophilic and high-conductive surface

[0025] Pre-treatment: take a piece of polycrystalline industrial silicon wafer, and sequentially clean it with acetone and ethanol for 10 minutes each, then rinse it with deionized water and dry it with nitrogen.

[0026] Plasma treatment: place the cleaned silicon wafer in the vacuum chamber of an inductively coupled plasma (ICP) device. After vacuumizing to a background pressure below 5 Pa, introduce a mixed gas of argon (Ar) and nitrogen (N2) with an Ar / N2 flow ratio of 4:1, and maintain the working pressure at 20 Pa. Turn on the ICP source, set the power to 800 W, the frequency to 13.56 MHz, and the processing time to 5 minutes.

[0027] Post-treatment: after the treatment, cool it down to room temperature in a vacuum environment and take it out.

[0028] Performance characterization: after testing, the water contact angle of the surface of the modified silicon wafer is reduced from about 70° to below 8°, showing super-hydrophilicity. At the same time, the surface square resistance is about 80 Ω / □ measured by the four-probe method, realizing high conductivity compared with the untreated silicon wafer (high resistivity, almost insulating). Analysis shows that argon plasma plays a role in sputter cleaning and activation of the surface, while nitrogen plasma realizes nitriding reaction on the activated surface, forming a conductive silicon nitride nano-layer, and at the same time introducing polar groups, which improves the hydrophilicity.

[0029] Example 2: Preparation of high-temperature oxidation-resistant and controllable hydrophobic surface

[0030] Pre-treatment: same as example 1.

[0031] Plasma treatment: The silicon wafer was placed in a plasma enhanced chemical vapor deposition (PECVD) chamber. A mixture of argon (Ar) and oxygen (O2) was introduced into the chamber at a flow ratio of 9:1 and a working pressure of 30 Pa. A pulsed radio frequency power source was used with an average power of 300 W, a pulse duty cycle of 50%, and a frequency of 13.56 MHz. The treatment time was 15 minutes.

[0032] Post-treatment: Same as Example 1.

[0033] Performance characterization: The modified silicon wafer showed a reduction of about 40% in the oxidation weight gain per unit area after being placed in static air at 800°C for 1 hour, demonstrating good high-temperature oxidation resistance. By adjusting the O2 ratio, the surface water contact angle can be controlled within the range of 30° to 100°. X-ray photoelectron spectroscopy (XPS) analysis showed that a dense non-stoichiometric silicon oxide (SiO_x, x<2) film was formed on the surface, which effectively blocked the diffusion of oxygen, and the surface terminal groups determined the degree of hydrophobicity.

[0034] Comparative Example

[0035] The same industrial silicon wafer was treated with a single oxygen plasma (power 300 W, pressure 30 Pa, time 15 minutes). The treated silicon wafer showed hydrophilic properties (contact angle about 15°), but the surface resistance was still extremely high, and after oxidation at 800°C, the weight gain was only reduced by about 10% compared to the untreated sample, with limited improvement in oxidation resistance. This comparison shows that a single gas plasma is difficult to achieve multifunctional integration, and the synergistic effect of multiple components described in the present application is the key to achieving multifunctionalization.

[0036] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents, in general, if a person skilled in the art is inspired by the disclosure, without departing from the purpose of the present application, without creative design, similar structure and embodiments of the technical scheme should belong to the protection scope of the present application.

Claims

1. A method for industrial silicon surface modification based on plasma-assisted technology, characterized in that, Includes the following steps: (a) Placing an industrial silicon substrate in the vacuum reaction chamber of a plasma processing device; (b) Introducing a multi-component mixed gas consisting of at least two gases into the vacuum reaction chamber; (c) Excite plasma and modify the surface of industrial silicon by adjusting the power and frequency of the plasma source, the proportion and flow rate of the multi-component mixed gas, and the processing time. (d) By utilizing the synergistic effect between different physical and chemical processes in the multi-component mixed gas plasma, a nanocomposite structure is formed in situ on the surface of industrial silicon, thereby simultaneously endowing the surface of industrial silicon with at least two functional properties; the functional properties are selected from superhydrophilicity, high temperature oxidation resistance, high conductivity, controllable hydrophobicity / superhydrophobicity, and catalytic activity.

2. The method for industrial silicon surface modification based on plasma-assisted technology according to claim 1, characterized in that, The multi-component gas mixture includes at least two combinations of argon, oxygen, nitrogen, hydrogen, carbon tetrafluoride, methane, and ammonia.

3. The method for industrial silicon surface modification based on plasma-assisted technology according to claim 1, characterized in that, In step (c), the power range of the plasma source is 50W to 5000W, the frequency is 13.56MHz to 2.45GHz, and the processing time is 10 seconds to 60 minutes.

4. The method for industrial silicon surface modification based on plasma-assisted technology according to claim 1, characterized in that, The in-situ formed nanocomposite structure in step (d) includes a composite layer formed by embedding metal or non-metal compound nanoparticles generated by oxidation, nitriding or carbonization reactions into the silicon surface.

5. The method for industrial silicon surface modification based on plasma-assisted technology according to claim 1, characterized in that, After step (a) and before step (b), the process further includes a pretreatment step of the industrial silicon substrate, the pretreatment including at least one of mechanical polishing, chemical cleaning or ultrasonic cleaning, to remove surface contaminants and the natural oxide layer.

6. The method for industrial silicon surface modification based on plasma-assisted technology according to claim 1, characterized in that, In step (c), a pulsed plasma mode is used, and the process parameters are adjusted in real time by monitoring the plasma emission spectrum to ensure the uniformity of the process.

7. The method for industrial silicon surface modification based on plasma-assisted technology according to claim 1, characterized in that, In step (d), the superhydrophilicity is characterized by a water contact angle of less than 10°; the high conductivity is characterized by a surface sheet resistance of less than 100Ω / □.

8. The method for industrial silicon surface modification based on plasma-assisted technology according to claim 1, characterized in that, In step (d), the high-temperature oxidation resistance is demonstrated by the modified industrial silicon exhibiting a reduction of more than 30% in oxidative weight gain per unit area compared to the unmodified sample after being kept at 800°C in static air for 1 hour.

9. The method for industrial silicon surface modification based on plasma-assisted technology according to claim 1, characterized in that, The modified industrial silicon material prepared by the method is suitable for photovoltaic cells, electronic packaging, or chemical catalysis.